\begin{table}[ht] \centering
\newcolumntype{R}{>{\raggedleft\arraybackslash}X}
\newcolumntype{L}{>{\raggedright\arraybackslash}X}
\newcolumntype{C}{>{\centering\arraybackslash}X}

\caption{Test}
\label{tab:abi_denv}
{\scriptsize
\begin{tabularx}{\raggedleft}{@{}lCCCC@{}}

\toprule
&{(1)}&{(2)}&{(3)}&{(4)} \tabularnewline \midrule
{}&{}&{}&{}&{} \tabularnewline
\midrule \addlinespace[\belowrulesep]
Age enrollment 20--25 Months Mean&0.144&0.966&5.397&1.056 \tabularnewline
Age enrollment 9--15 Months Mean&0.167&0.891&6.131&0.950 \tabularnewline
P-value&\textbf\{(0.000)\}&\textbf\{(0.000)\}&\textbf\{(0.000)\}&\textbf\{(0.000)\} \tabularnewline
N&1.9e+04&4.8e+04&4.8e+04&4.8e+04 \tabularnewline
Age enrollment 15--20 Months Mean&0.157&0.919&5.613&0.990 \tabularnewline
Age enrollment 9--15 Months Mean&0.167&0.891&6.131&0.950 \tabularnewline
P-value&\textbf\{(0.000)\}&\textbf\{(0.000)\}&\textbf\{(0.000)\}&\textbf\{(0.000)\} \tabularnewline
N&2.2e+04&5.2e+04&5.2e+04&5.2e+04 \tabularnewline
Age enrollment 20--25 Months Mean&0.144&0.966&5.397&1.056 \tabularnewline
Age enrollment 15--20 Months Mean&0.157&0.919&5.613&0.990 \tabularnewline
P-value&\textbf\{(0.000)\}&\textbf\{(0.000)\}&\textbf\{(0.004)\}&\textbf\{(0.000)\} \tabularnewline
N&1.6e+04&4.5e+04&4.5e+04&4.5e+04 \tabularnewline
\bottomrule \addlinespace[\belowrulesep]

\end{tabularx}
\\ \parbox{\raggedleft}{\scriptsize Note:}
}
\end{table}
